5 standards that every electrical project manager should know
In electrical engineering, there are many standards to consider when using plastics to insulate or fasten components. Project managers should be familiar with these in order to select the right material. Here we present the most important standards and briefly explain what they regulate in detail.
Many requirements for engineering plastics in electrical engineering result from regulations and standards. How must the material behave in the event of fire? How safe must the plastic be against electric shock? Are there special requirements for leakage current? What about substances that are hazardous to health?
Standards ensure that the materials and substances we use to make plastic profiles have clearly defined properties. This makes it possible to find the right material for every requirement in a project. You don't have to decide which material to use on a case-by-case basis. As your implementation partner, we will do that for you. However, it is worth having a rough idea of which standards are relevant and what they cover.
Some of the standards described below refer explicitly to the materials, in our case plastics, while others refer to the finished product, which is made from engineering plastics. The flammability and insulation properties of plastics are particularly important for use in electrical engineering.
1. Flammability: UL94
This Underwriters Laboratories (UL) standard describes a method for evaluating and classifying the flammability of plastics. The classes are as follows:
| Class | Requirement |
|---|---|
| HB75 | Horizontal burning test - for thickness <3 mm; rate <75 mm/min. |
| HB 40 | Horizontal burning test - for thickness 3-13 mm; rate <40 mm/min. |
| V-2 | Vertical burning test - extinguished within 30 seconds, dripping of molten plastic allowed. |
| V-1 | Same as V-2, but no burning dripping of molten plastic allowed; maximum afterglow 60 seconds. |
| V-0 as V-1 | but flame extinguished within 10 seconds; maximum afterglow 30 seconds. |
| 5VB at least V-2 | additionally tested with the 500 watt flame (125 mm flame height); flame five times for five seconds each, no dripping permitted. |
| 5VA as 5VB | additionally tested with a plate clamped horizontally; no dripping or burning holes > 1 mm in diameter allowed. |
2. Protection against electric shock: DIN EN 61140 / VDE 0140-1
This standard is designed to protect people and animals. Electrical equipment that can be insulated with plastic components can be categorised and labelled according to four different protection classes. Class 2 and 3 have particularly high requirements for the insulation of the component.
| Class | Requirement |
|---|---|
| 0 | Basic insulation; no special protection against electric shock |
| 1 | Protective conductor; all electrically conductive parts of the enclosure of the equipment are connected to the protective conductor |
| 2 | Protective insulation; reinforced or double insulation at the level of the rated insulation voltage between active and touchable parts |
| 3 | Tracking resistance; DIN IEC 60112 |
3. Tracking resistance:
DIN IEC 60112
While the internal insulation properties of a plastic are determined by its specific electrical resistance, current conduction on the surface can differ significantly from this. Tracking resistance describes the insulation resistance of the surface of insulating materials, particularly when exposed to moisture and contamination.
DIN IEC 60112 defines the maximum creepage current that can occur under standardised test conditions in a defined test arrangement. The comparative tracking index (CTI) and the proof tracking index (PTI) are used as parameters to characterise the tracking resistance.
4. Groups of insulating materials:
DIN EN 50124
Based on the CTI values according to DIN IEC 60112, plastics can be divided into insulation groups:
- Insulation group Re
- I 600 ≤ CTI
- II 400 ≤ CTI < 600
- IIIa 175 ≤ CTI < 400 (FR4)
- IIIb 100 ≤ CTI < 175
5. Halogen free:
DIN IEC 61249-2-21
Bromine and chlorine can form corrosive, toxic compounds, especially in the event of fire. For this reason, halogen-free materials are increasingly being used in electrical engineering. The International Electrotechnical Commission (IEC) defines halogen-free based on the amount of chlorine and bromine in the plastic.
A product is considered halogen-free if the following limits are met
- 900 ppm chlorine
- 900 ppm bromine
- 1,500 ppm total halogens
The standards described above define the requirements to be met in electrical engineering.
